It is known a method for telomerizing vinylidene fluoride using a perfluoroalkyl iodide as a starting raw material and a metal or metal complex as a catalyst. In addition, it is known a method for performing telomerization in the presence of a radical generator under a high temperature, a high pressure, or a high temperature and a high pressure condition. A reaction under a high temperature and/or a high pressure needs a large amount of energy. Furthermore, corrosion of facilities due to hydrofluoric acid or the like that is generated during the reaction becomes serious, and thereby the frequency of renewal of the facilities is increased. On the other hand, when a corrosion resistant material is used, since such a material is expensive, it cannot be avoided that the facilities are expensive.    [Patent Document 1] JP-A-60-106533    [Patent Document 2] JP-A-60-104023    [Non-Patent Document 1] J. Fluorine Chem., 70, 215 (1995)    [Non-Patent Document 2] J. Fluorine Chem., 102, 253 (2000)
It has been reported that compounds of which telomer-terminal perfluoroalkyl group having about 8 carbon atoms obtained in the above have high bioaccumulation potential and have an environmental problem. Therefore, it is concerned that the manufacturing and the use of these compounds will become difficult in the future. However, compounds including perfluoroalkyl groups having 6 or less carbon atoms are recognized to be low in bioaccumulation potential.